OpenAI Responses API Support

/v1/responses Endpoint Introduction

LaoZhang API fully supports OpenAI’s latest Responses API, the next-generation agent-building interface introduced in March 2025. Responses API combines the simplicity of Chat Completions with the tool usage and state management capabilities of Assistants API, providing developers with a more flexible and powerful AI application development experience.

Next-Gen API: Responses API is a superset of Chat Completions, providing all Chat Completions features plus advanced capabilities like built-in tools and state management. However, it only supports select new OpenAI models - see details below.

Core Features

Built-in Tool Support

Rich tools including web search, file search, code interpreter, function calling

State Management

Maintain conversation context and state via previous_response_id

Reasoning Persistence

O3/O4-mini reasoning tokens persist across requests

Full Compatibility

Supports all tool-capable GPT-4.1 and O3 series models

Supported Models

Reasoning Models (Recommended)

O3 Series: o3, o3-pro, o4-mini
Features: Reasoning tokens persist across requests for smarter contextual understanding

Conversational Models

GPT-4.1 Series: gpt-4.1, gpt-4.1-mini
Features: Powerful tool calling and multimodal capabilities

Model Requirements: Only newer models support the /v1/responses endpoint. Legacy models like GPT-3.5 do not support this interface.

Basic Usage

Simple Conversation

curl https://api2.laozhang.ai/v1/responses \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -d '{
    "model": "gpt-4.1",
    "input": "Hello! How can you help me today?",
    "instructions": "You are a helpful assistant."
  }'

from openai import OpenAI

client = OpenAI(
    api_key="YOUR_API_KEY",
    base_url="https://api2.laozhang.ai/v1"
)

response = client.responses.create(
    model="gpt-4.1",
    input="Hello! How can you help me today?",
    instructions="You are a helpful assistant."
)

print(response.output[0].content[0].text)

import OpenAI from 'openai';

const openai = new OpenAI({
  apiKey: 'YOUR_API_KEY',
  baseURL: 'https://api2.laozhang.ai/v1'
});

const response = await openai.responses.create({
  model: 'gpt-4.1',
  input: 'Hello! How can you help me today?',
  instructions: 'You are a helpful assistant.'
});

console.log(response.output[0].content[0].text);

Actual Response Example

Complete response format:

{
  "id": "resp_6884fcab4930819dbbc02f15cbe63f6c0a92c38ff214d10a",
  "object": "response",
  "created_at": 1753545899,
  "status": "completed",
  "background": false,
  "error": null,
  "incomplete_details": null,
  "instructions": "You are a helpful assistant.",
  "max_output_tokens": null,
  "max_tool_calls": null,
  "model": "gpt-4.1-2025-04-14",
  "output": [
    {
      "id": "msg_6884fcab8f18819dbcdf349f01b424f80a92c38ff214d10a",
      "type": "message",
      "status": "completed",
      "content": [
        {
          "type": "output_text",
          "annotations": [],
          "logprobs": [],
          "text": "Hello! How can I assist you today?"
        }
      ],
      "role": "assistant"
    }
  ],
  "parallel_tool_calls": true,
  "previous_response_id": null,
  "prompt_cache_key": null,
  "reasoning": {
    "effort": null,
    "summary": null
  },
  "safety_identifier": null,
  "service_tier": "default",
  "store": true,
  "temperature": 1.0,
  "text": {
    "format": {
      "type": "text"
    }
  },
  "tool_choice": "auto",
  "tools": [],
  "top_logprobs": 0,
  "top_p": 1.0,
  "truncation": "disabled",
  "usage": {
    "input_tokens": 19,
    "input_tokens_details": {
      "cached_tokens": 0
    },
    "output_tokens": 10,
    "output_tokens_details": {
      "reasoning_tokens": 0
    },
    "total_tokens": 29
  },
  "user": null,
  "metadata": {}
}

Request Parameters

Required Parameters

Parameter	Type	Description
`model`	string	Model name, e.g., `gpt-4.1`, `o3`
`input`	string	User input content

Optional Parameters

Parameter	Type	Default	Description
`instructions`	string	null	System instructions defining assistant behavior
`previous_response_id`	string	null	Previous response ID for context maintenance
`temperature`	float	1.0	Controls output randomness (0-2)
`max_output_tokens`	int	null	Maximum output tokens
`tools`	array	[]	Available tools list
`tool_choice`	string	”auto”	Tool selection strategy
`parallel_tool_calls`	boolean	true	Allow parallel tool calls
`store`	boolean	true	Store conversation for training
`metadata`	object	Custom metadata

Built-in Tool Support

1. Function Calling

response = client.responses.create(
    model="gpt-4.1",
    input="What's the weather like in New York?",
    instructions="You are a helpful weather assistant.",
    tools=[
        {
            "type": "function",
            "function": {
                "name": "get_weather",
                "description": "Get current weather for a city",
                "parameters": {
                    "type": "object",
                    "properties": {
                        "city": {
                            "type": "string",
                            "description": "City name"
                        }
                    },
                    "required": ["city"]
                }
            }
        }
    ]
)

2. Code Interpreter

response = client.responses.create(
    model="gpt-4.1",
    input="Create a chart showing sales data: Jan:100, Feb:150, Mar:120",
    instructions="You are a data analyst. Use code interpreter to create visualizations.",
    tools=[{"type": "code_interpreter"}]
)

3. File Search

response = client.responses.create(
    model="gpt-4.1",
    input="Search for information about quarterly reports",
    instructions="You are a document analyst.",
    tools=[{"type": "file_search"}]
)

State Management

Maintaining Conversation Context

{/* First conversation round */}
response1 = client.responses.create(
    model="gpt-4.1",
    input="The active project code is Atlas. Please remember this.",
    instructions="You are a helpful assistant with good memory."
)

{/* Second round - use previous_response_id to maintain context */}
response2 = client.responses.create(
    model="gpt-4.1",
    input="What is the active project code?",
    instructions="You are a helpful assistant with good memory.",
    previous_response_id=response1.id
)

print(response2.output[0].content[0].text)  {/* Should answer "Atlas" */}

Multi-turn Tool Calling

def multi_turn_conversation():
    response_id = None

    for user_input in ["What's 2+2?", "Now multiply that by 3", "And divide by 2"]:
        response = client.responses.create(
            model="o3",
            input=user_input,
            instructions="You are a math tutor. Show your reasoning.",
            previous_response_id=response_id,
            tools=[{"type": "code_interpreter"}]
        )

        print(f"User: {user_input}")
        print(f"Assistant: {response.output[0].content[0].text}")

        response_id = response.id  {/* Maintain context */}

Reasoning Model Features

O3/O4-mini Reasoning Persistence

Reasoning models have special advantages in Responses API:

{/* Use O3 for complex reasoning */}
response = client.responses.create(
    model="o3",
    input="Solve this step by step: If a train travels 120km in 2 hours, then speeds up 20% for the next hour, how far did it travel in total?",
    instructions="Think through this problem step by step, showing all reasoning."
)

{/* View reasoning process */}
reasoning_tokens = response.usage.output_tokens_details.reasoning_tokens
print(f"Reasoning tokens used: {reasoning_tokens}")

{/* Continue conversation, reasoning context persists */}
follow_up = client.responses.create(
    model="o3",
    input="Now what if the train slowed down 10% in the fourth hour?",
    previous_response_id=response.id
)

Comparison with Chat Completions

Feature	Chat Completions	Responses API
Basic Conversation	✅ Supported	✅ Supported
Streaming	✅ Supported	✅ Supported
Function Calling	✅ Supported	✅ Enhanced
Built-in Tools	❌ Not supported	✅ Rich tools
State Management	❌ Stateless	✅ Stateful
Reasoning Persistence	❌ Not supported	✅ O3/O4 support
File Search	❌ Not supported	✅ Supported
Code Interpreter	❌ Not supported	✅ Supported

Migration Example

Migrating from Chat Completions to Responses API:

{/* Old way */}
response = client.chat.completions.create(
    model="gpt-4.1",
    messages=[
        {"role": "system", "content": "You are a helpful assistant."},
        {"role": "user", "content": "Hello!"}
    ]
)
content = response.choices[0].message.content

{/* New way */}
response = client.responses.create(
    model="gpt-4.1",
    input="Hello!",
    instructions="You are a helpful assistant."
)
content = response.output[0].content[0].text

Advanced Features

Parallel Tool Calling

response = client.responses.create(
    model="gpt-4.1",
    input="Get weather for New York and Los Angeles, then calculate travel time between them",
    instructions="You are a travel assistant.",
    parallel_tool_calls=True,
    tools=[
        {"type": "function", "function": {"name": "get_weather", ...}},
        {"type": "function", "function": {"name": "calculate_distance", ...}}
    ]
)

Output Format Control

response = client.responses.create(
    model="gpt-4.1",
    input="Summarize this data in JSON format",
    instructions="Always respond in valid JSON.",
    text={
        "format": {
            "type": "json_object"
        }
    }
)

Reasoning Effort Control (O3 Series)

response = client.responses.create(
    model="o3",
    input="Solve this complex physics problem",
    instructions="Think carefully and show detailed reasoning.",
    reasoning={
        "effort": "high"  {/* low, medium, high */}
    }
)

Response Fields

Core Fields

Field	Type	Description
`id`	string	Response unique identifier
`object`	string	Fixed as “response”
`created_at`	integer	Creation timestamp
`status`	string	Status: completed/failed/in_progress
`model`	string	Actual model version used
`output`	array	Output message array
`usage`	object	Token usage statistics

Output Message Format

{
  "id": "msg_xxx",
  "type": "message",
  "status": "completed",
  "content": [
    {
      "type": "output_text",
      "text": "Response content",
      "annotations": [],
      "logprobs": []
    }
  ],
  "role": "assistant"
}

Usage Statistics

{
  "usage": {
    "input_tokens": 19,
    "input_tokens_details": {
      "cached_tokens": 0
    },
    "output_tokens": 10,
    "output_tokens_details": {
      "reasoning_tokens": 0  {/* Only for reasoning models */}
    },
    "total_tokens": 29
  }
}

Error Handling

Standard Error Format

{
  "error": {
    "type": "invalid_request_error",
    "code": "model_not_supported",
    "message": "The model 'gpt-3.5-turbo' is not supported for the responses endpoint.",
    "param": "model"
  }
}

Common Errors

Error Code	Description	Solution
`model_not_supported`	Model doesn’t support Responses API	Use supported newer models
`invalid_previous_response_id`	Invalid previous response ID	Check response ID is correct
`tool_not_available`	Tool unavailable	Check tool configuration
`max_tokens_exceeded`	Token limit exceeded	Reduce input or set max_output_tokens

Best Practices

1. State Management Strategy

class ConversationManager:
    def __init__(self, model="gpt-4.1", instructions="You are a helpful assistant."):
        self.model = model
        self.instructions = instructions
        self.last_response_id = None

    def send_message(self, input_text, tools=None):
        response = client.responses.create(
            model=self.model,
            input=input_text,
            instructions=self.instructions,
            previous_response_id=self.last_response_id,
            tools=tools or []
        )

        self.last_response_id = response.id
        return response.output[0].content[0].text

    def reset_conversation(self):
        self.last_response_id = None

{/* Usage example */}
conv = ConversationManager()
print(conv.send_message("The active project code is Atlas"))
print(conv.send_message("What is the active project code?"))  {/* Will remember project code Atlas */}

2. Tool Calling Optimization

def smart_tool_calling(user_input):
    {/* Intelligently select tools based on input */}
    available_tools = []

    if "weather" in user_input.lower():
        available_tools.append(weather_tool)
    if "calculate" in user_input.lower():
        available_tools.append(calculator_tool)
    if "search" in user_input.lower():
        available_tools.append(search_tool)

    response = client.responses.create(
        model="gpt-4.1",
        input=user_input,
        instructions="Use the appropriate tools to help the user.",
        tools=available_tools,
        tool_choice="auto"
    )

    return response

3. Reasoning Model Optimization

def optimized_reasoning(complex_problem):
    response = client.responses.create(
        model="o3",
        input=complex_problem,
        instructions="Think step by step and show your reasoning process.",
        reasoning={
            "effort": "high"  {/* Use high reasoning effort for complex problems */}
        },
        temperature=0.1  {/* Lower randomness for consistent results */}
    )

    {/* Analyze reasoning usage */}
    reasoning_tokens = response.usage.output_tokens_details.reasoning_tokens
    total_cost = calculate_cost(response.usage)

    return {
        "answer": response.output[0].content[0].text,
        "reasoning_tokens": reasoning_tokens,
        "cost": total_cost
    }

Future Development

Upcoming Features

Full Assistants API feature integration (H1 2026)
More built-in tools: Web search, computer use, etc.
Model Context Protocol (MCP) support
Enhanced multimodal capabilities

Migration Timeline

Now: Can start using Responses API
H1 2026: Feature parity with Assistants API
2026: Assistants API deprecation announcement
2027: Complete migration to Responses API

Development Recommendation: New projects should use Responses API directly, existing projects can migrate gradually. LaoZhang API will continue to follow OpenAI updates to ensure feature completeness.

Need more help? Visit LaoZhang API or check OpenAI Responses API Official Documentation.

​/v1/responses Endpoint Introduction

​Core Features

Built-in Tool Support

State Management

Reasoning Persistence

Full Compatibility

​Supported Models

​Reasoning Models (Recommended)

​Conversational Models

​Basic Usage

​Simple Conversation

​Actual Response Example

​Request Parameters

​Required Parameters

​Optional Parameters

​Built-in Tool Support

​1. Function Calling

​2. Code Interpreter

​3. File Search

​State Management

​Maintaining Conversation Context

​Multi-turn Tool Calling

​Reasoning Model Features

​O3/O4-mini Reasoning Persistence

​Comparison with Chat Completions

​Migration Example

​Advanced Features

​Parallel Tool Calling

​Output Format Control

​Reasoning Effort Control (O3 Series)

​Response Fields

​Core Fields

​Output Message Format

​Usage Statistics

​Error Handling

​Standard Error Format

​Common Errors

​Best Practices

​1. State Management Strategy

​2. Tool Calling Optimization

​3. Reasoning Model Optimization

​Future Development

​Upcoming Features

​Migration Timeline

/v1/responses Endpoint Introduction

Core Features

Supported Models

Reasoning Models (Recommended)

Conversational Models

Basic Usage

Simple Conversation

Actual Response Example

Request Parameters

Required Parameters

Optional Parameters

Built-in Tool Support

1. Function Calling

2. Code Interpreter

3. File Search

State Management

Maintaining Conversation Context

Multi-turn Tool Calling

Reasoning Model Features

O3/O4-mini Reasoning Persistence

Comparison with Chat Completions

Migration Example

Advanced Features

Parallel Tool Calling

Output Format Control

Reasoning Effort Control (O3 Series)

Response Fields

Core Fields

Output Message Format

Usage Statistics

Error Handling

Standard Error Format

Common Errors

Best Practices

1. State Management Strategy

2. Tool Calling Optimization

3. Reasoning Model Optimization

Future Development

Upcoming Features

Migration Timeline